Characterization of the stemphylium blight pathogens and their effect on lentil yield
Caudillo Ruiz, Kiela B 1979-
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The disease stemphylium blight has become common in lentil fields in Saskatchewan, but the effect of this disease on developing lentil plants, has not been studied under field conditions. Even though Stemphylium botryosum is suspected to be the pathogen causing stemphylium blight in lentil around the world, there is no confirmation of the pathogenic species involved in stemphylium blight of lentil in Saskatchewan. The objectives of this study were to determine the effect on lentil seed quantity and quality of S. botryosum infection at the seedling, the early-flowering, the mid-flowering or the podding stages, and to characterize the pathogen or pathogens causing stemphylium blight in Saskatchewan lentil fields. Three field experiments were conducted over two years using green polyethylene low tunnels to create conducive environments and control the timing of infection. Cumulative disease severity, measured as area under the disease progress curve, in lentil treatments inoculated at the seedling stage was higher compared to treatments inoculated at later growth stages or to uninoculated control treatments, in which some stemphylium blight developed due to natural inoculum. Neither the amount of harvested seed, nor seed weight or seed size were reduced compared to the uninoculated control, even though disease severity was higher in inoculated versus uninoculated treatments. Seed infection levels of 2.6 to 3.4% in seed harvested from treatments that were inoculated at the seedling, early and mid-flower stages were significantly higher than those observed in seeds from uninoculated control treatments (0.6%) or from treatments inoculated at podding (1.2%). Field isolates of Stemphylium spp. were compared to the ex-type isolate by morphology, and additionally to sequence data of five Stemphylium spp. and one Alternaria sp. obtained from GenBank by molecular phylogenetic analyses of the internal transcribe spacer (ITS) and the glyceraldehyde 3 – phosphate dehydrogenase (gpd) gene regions. Morphology of colony and conidia were not informative since features overlapped except for three isolates. Results of the molecular phylogenetic analyses revealed that S. botryosum is one of two possible Stemphylium spp. involved in the development of stemphylium blight in lentil. The three isolates with different morphology were also consistently clustered as a species distinct from the Stemphylium species. Although yield loss could not be demonstrated here, further studies on the epidemiology of the pathogens causing stemphylium blight in Saskatchewan lentil fields are warranted in view of the fact that more than one candidate species was identified as the causal agent.
DegreeMaster of Science (M.Sc.)
DepartmentAgricultural and Bioresource Engineering
CommitteeKutcher, Randy; Shirtliffe, Steve; Chongo, Godfrey; Bai, Yuguang
Copyright DateJuly 2016